Just One Second!

Photonics SpectraJul 1997
To keep the world's atomic clocks synchronized with the Earth's rotation, the NationalInstitute of Standards and Technology's Time and Frequency Div. added a "leap" second June 30. This is the 21st adjustment to the world's time scale since 1972 when leap seconds were first added. The planet loses several thousandths of a second each day, which necessitates leap seconds.